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Heat waves and dehydration in the elderly

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Sir,
I read with interest the article by Olde Rikkert, et. al on the dangers of
heat waves and dehydration in frail older people. For several years I have
taught my trainees the importance of monitoring long-range weather
forecasts in the acute care of frail older people. Prior awareness of the
likelihood of prolonged hot weather allows for preventative action to be
taken in reducing or stopping diuretics , ACE-inhibitors and NSAIDs in
frail vulnerable older people in our acute hospital, most of whom barely
manage to maintain adequate fluid intake in normal climatic conditions.
Staff are particularly asked to consider the possibility of a heatwave at
week-ends and over Bank Holiday weekends, when medical supervision is
minimal.

More recently I have extended this teaching to general practitioner
colleagues caring for the most vulnerable older people - those in care
homes or those living alone and in receipt of home care.

Most of those who are at greatest risk from dehydration during a
heatwave are known to older people's services and so preventative action
is possible if only we seek to prevent problems rather than waiting for
the crisis to happen!

Dehydration in the frail elderly population is a major health issue.
This becomes particularly obvious during hot summers. But regardless of
season, dehydration is one of the most frequent diagnoses leading to
hospitalization in the frail elderly with a high mortality rate (1). If a
frail old person presents with an acute or subacute decline of cognitive
or physical function, dehydration is among the reasons most often to blame
for. The management of acutely unwell old peolple, already too weak to
receive oral fluids, presents a common challenge to medical and nursing
home staff (2). In their important editorial (3), Olde-Rikkert and
colleagues miss the opportunity to reintroduce hypodermoclysis
(subcutaneous infusion), an ingenious technique for prevention and
treatment of dehydration. In confused and agitated elderly patients,
hypodermoclysis has been shown to be safer and more effective than the
intravenous route. Hypodermoclysis can easily be administered in non-
hospital settings and, thus, may reduce hospital admissions due to
dehydration. Hypodermoclysis, although simple, safe and (cost) effective,
is grossly underused as a method of fluid delivery for the frail elderly.
By promoting this technique, editorialists and opinion leaders could
contribute to older people being no longer “denied an element of health
care that they are perhaps most well suited to.” (4)

Olde Rikkert and colleagues rightly raise the importance of
recognising dehydration in older people but their assertion that
Parkinson's disease (PD) drugs should be reconsidered, stopped or their
doses reduced needs to be challenged 1.

Missed (or even reduced) doses of dopaminergic agents such as
levodopa or dopamine agonists have been associated with the potentially
life-threatening condition neuroleptic malignant-like syndrome (NMLS) 2,3.
This condition, which is associated with confusion, rigidity, pyrexia and
elevated muscle enzymes, is more likely in dehydrated individuals and
during hot weather 4,5.
In recognition of this issue and other problems faced when inpatients with
PD do not receive the correct medication, the Parkinson's Disease Society
has been running the 'Get it on time' campaign to raise awareness in the
medical and nursing professions 6.

In the absence of evidence that those with Parkinson's disease
require less treatment in hot weather and an established link between
reduced PD drugs and NMLS the advice for this group of patients should be
to continue their usual therapy (unless they are advised by a movement
disorder specialist that they are over-medicated) and the focus should be
on ensuring adequate hydration. Any other approach could have the
potential to undermine the important message that Parkinson's patients
require the correct treatment every time.

In their interesting contribution, Sommet et al failed to address the
question, "What are the pathophysiological consequences of dehydration ?"
The question is of particular relevance as their observations concerned
patients aged 75 years and older. In 1989, Ajmani and Rifkind from the
Institute of Aging, reported that as a part of the aging process, blood
viscosity increased, probably as a consequence of raised levels of
fibrinogen. As a result, tissue perfusion was compromised.

Because dehydration will amplify the blood viscosity problem
with potentially lethal consequences, it would seem essential that the
blood viscosity/dehydration problem be addressed promptly.

The elderly need special care, because they are paradoxically frail but sturdy
survivors who have not succumbed to life's many perils. So as physicians, we
should respect the durability and success of their homeostatic mechanisms and
minimize our pharmaceutical interventions. For example, when treating the
elderly for dependent ankle edema due to venous incompetence, it is best to
avoid diuretics and instead use compression stockings and exercise. This will
reduce the likelihood of dehydration, with all its sequelae, including heat
exhaustion and heat stroke.

We read with great interest the editorial from Olde Rikkert et al1 on
heat waves and dehydration in the elderly. As mentioned by the authors,
the exceptional heat wave in 2003 leaded to an excess mortality, in
particular in old people. In France for example, this heat wave was
associated with about 14800 deaths, mainly among people over 70 years.2

Since there are interactions between physiological dysfunctions
induced by heat and drugs, some pharmacological classes may represent a
risk factor of morbi-mortality during heat waves. Few studies have
investigated the role of drugs in sanitary consequences of heat waves. In
order to evaluate this relation, we performed a study in the French
Pharmacovigilance Database to evaluate adverse drug reactions (ADRs) in
patients older than 70 years reported during the 2003 summer to the French
Network of Pharmacovigilance Centers.3 Sixty-eight “serious” ADRs related
to heat occurred in patients older than 70 years were registered in the
French Pharmacovigilance Database during summer 2003. These ADRs were
mainly metabolic (dehydration, hydroelectrolytic disorders) and
neuropsychiatric (confusion, disorientation, coma). Drugs more frequently
involved were diuretics, angiotensin converting enzyme inhibitors,
serotoninergic antidepressants, proton pump inhibitors, digoxin,
benzodiazepines and sartans.

The involvement of diuretics underlines that dehydration represents
the main pathophysiological problem during unexpected warm periods.
Angiotensin converting enzymes inhibitors and sartans induce hyponatremia,
arterial hypotension and renal insufficiency. Apart from their action on
hydro electrolytic movements and renal metabolism, these drugs, as
serotonin-reuptake inhibitors, could also modify water ingestion through a
central effect. Hyponatremia and confusion was also described with proton
pump inhibitors, especially in elderly people. Confusion and
disorientation could be partly explained by digoxin and benzodiazepine
exposure. However, because of their pharmacodynamic and pharmacokinetic
properties, other pharmacological classes could interfere with
thermoregulation processes. Antipsychotics, H1 antihistamine and
imipraminic drugs are known to disturb central thermoregulation by their
action on hypothalamic centres. Drugs leading to a sweating decrease -
mainly atropinic drugs and carbonic anhydrase inhibitors - reduce the
capacity for heat loss. Drugs leading to vasoconstriction, as
sympathomimetic and beta-blocking agents, reduce heat loss by convection.

In order to better investigate and quantify the risk of different
pharmacological classes during heat waves among other risk factors,
pharmacoepidemiological studies should be performed. In summer 2007,
French Medicament Agency supported a multicentric case-control pilot study
called SIRIUS to evaluate in real conditions the role of drugs in heat-
related adverse effects.4 Drugs exposure in patients older than 65 years
hospitalized with hyperthermia or dehydration were compared with
controls. Since there was no heat wave during this period, this study
suffers from a lack of power. However, similar methodology will be used in
further studies in case of new heat wave’s occurrence.

Results of such studies could help physicians to reconsider patients’
treatments during a heat wave, and inform patients at risk and their
family of these drug-related dangers.